Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context the annotations cannot carry: the free daily allowance and the $0.002 USDC x402 payment model, which directly affects how an agent should call it. It does not describe return payload shape, but an output schema exists, so that omission is acceptable.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three tight sentences: what the dataset means, how to address it, what it costs. The domain clarification is front-loaded and no sentence is filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With rich annotations, a 100%-covered 5-parameter schema, and an output schema, the description's remaining burden is light, and it covers purpose, addressing, and cost. It could have noted behaviour when no Article 4 direction applies to the point, which is the main practical uncertainty for a spatial lookup.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all five parameters (lat, lng, geometry, postcode, include_ended) are already documented in the schema. The description's 'By UK postcode or lat/lng' merely restates the two input modes and adds no format or constraint detail beyond the schema, so baseline 3 is correct.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names the specific dataset (Article 4 directions), the spatial scope ('covering a point'), and explains the domain meaning (permitted development rights removed, so more work needs planning permission). That is far more than the title restated. It stops short of 5 because it does not differentiate itself from potentially overlapping siblings such as uk-property__planning-constraints or uk-planning__designations.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

'By UK postcode or lat/lng' tells the agent how to address the query and the pricing line hints at cost-aware usage, but there is no explicit when-to-use statement, no exclusions, and no sibling alternative named. Usage is implied by the Article 4 definition rather than stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.